MIXED MESSAGES?
QMy Rover 25 hiccups occasionally, as though the ignition has cut out for a fraction of a second. Its idle occasionally rises to 1800rpm and can sometimes – but not always – be returned to normal with a blip of the throttle. Hiccuping seems to occur mainly at light throttle and lower rpm. A diagnostic test was inconclusive. Any ideas?
Michael Horsley, via email
AOur first suspect would be the throttle position sensor (TPS). It’s a potentiometer mounted on the throttle body that tells the ECU how far open the throttle is. It may wear out, work loose on the throttle body or spindle, or simply need its electrical connector cleaning.
An intermittent air leak might cause these symptoms. Check all vacuum and breather hoses, plus the hose to the Idle Air Control Valve on the inlet manifold.